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authorAndi Kleen <ak@linux.intel.com>2013-02-07 13:58:40 -0800
committerMichal Marek <mmarek@suse.cz>2013-02-22 13:45:56 +0100
commite82c4bb8b457926e13d4dd3aacbb8e573daede23 (patch)
treecc41684965e8efde6de455e5f67940ba814eafaf /Makefile
parent8937e897181a411f73faf4da83c452c7b0732929 (diff)
downloadlinux-e82c4bb8b457926e13d4dd3aacbb8e573daede23.tar.gz
Kbuild: Disable var tracking with CONFIG_DEBUG_INFO_REDUCED
Newer gcc enables the var-tracking pass with -g to keep track which registers contain which variables. This is one of the slower passes in gcc. With reduced debug info (aimed at objdump -S, but not using a full debugger) we don't need this fine grained tracking. But it was still enabled because -g was enabled. Disable it explicitely for DEBUG_INFO_REDUCED. On my 8T workstation this gives me about a 12 second gain in building a reasonable kernel config (2min16 vs 2min28) with DEBUG_INFO_REDUCED. With full DEBUG_INFO it takes 2min46 The actual improvement in user time taken by the compiler is much higher (all CPU combined user time 15min5s vs 16m30 before) but the usual amdahl bottleneck on the linker prevents more speedup. It still saves some more energy and keeps cycles for other things. Signed-off-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Michal Marek <mmarek@suse.cz>
Diffstat (limited to 'Makefile')
-rw-r--r--Makefile3
1 files changed, 2 insertions, 1 deletions
diff --git a/Makefile b/Makefile
index d4dd2e4a045..ece96fc01b3 100644
--- a/Makefile
+++ b/Makefile
@@ -618,7 +618,8 @@ KBUILD_AFLAGS += -gdwarf-2
endif
ifdef CONFIG_DEBUG_INFO_REDUCED
-KBUILD_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly)
+KBUILD_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \
+ $(call cc-option,-fno-var-tracking)
endif
ifdef CONFIG_FUNCTION_TRACER